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There are nuclides heavier than 56Fe, for which no decay mode is energetically allowed. 197Au is not one of them, because it could in principle do alpha decay.
by fsh 3y ago
There are nuclides heavier than 56Fe, for which no decay mode is energetically allowed. 197Au is not one of them, because it could in principle do alpha decay. Wikipedia has a long list of theoretically stable nuclides (no decay mode possible), and observationally stable nuclides (at least one decay mode possible, but not observed): https://en.wikipedia.org/wiki/List_of_nuclides https://en.wikipedia.org/wiki/List_of_nuclides
- jychang 3y agoAlso, proton decay is a thing. At a certain point, if the proton is unstable, the half life of the nucleus is longer than the proton itself.
- fsh 3y agoNo, it isn't. According to the Standard Model, the proton is stable at every time scale. And no proton decay has ever been observed.
- MichaelZuo 3y agoThe Standard Model that is known to be, at best, incomplete?
- jfengel 3y agoOnly in that it doesn't incorporate gravity. And given the extremely low energy scale of gravity, it's unlikely to make a difference here. There are extensions to the Standard Model being used to search for dark matter, but until one of those is actually found experimentally, you can't say that it makes the Standard Model incomplete. It's sound within its domain -- aggravatingly so, since that makes it really hard to figure out what's next.
- wiml 3y agoProton decay may be a thing but it's not predicted by current models. But similar to your example, neutron decay is a thing (a free neutron has a halflife of about 10 minutes), and yet many nuclei are stable for much longer.
- ISL 3y agoProton decay is predicted by many models -- it's the reason the first huge water-Cherenkov detectors were built. The surprising thing is that, for some reason, they've never been observed to decay.
- mensetmanusman 3y agoIf they can’t decay then time can’t stop.